This application claims the priority of German application 198 06 519.01, filed Feb. 17, 1998, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to an arrangement for sterilizing the inner surfaces as well as an area of the outer surfaces, located at a filling opening, of pressure sensitive, non electroconductive containers by means of a low-pressure plasma, comprising an evacuable chamber for taking up the containers. The arrangement comprises a vacuum pump for evacuating the chamber, a supply pipe for supplying gas to be ionized, which pipe is connected to the chamber, two electrodes which surround the containers with shell-like areas and which electrodes generate the plasma, the electrodes having a recess in the area of the filling opening, said recess having clearance in relation to the container, and a high frequency generator for applying an alternating voltage at one of the electrodes, one of which is grounded.
In the case of an arrangement of this type (U.S. Pat. No. 5,801,354), the electrodes are arranged in the inside of the chamber, so that the area outside of the electrodes must also be evacuated. This leads on the one hand to considerable mechanical complications and on the other to increased power consumption. The known arrangement is however advantageous in that, due to the electrodes which closely surround the container, the plasma is essentially only ignited in the inside of the container, so that the outer surfaces of the container, which are not to be sterilized, are not hit by the plasma. As the vacuum prevails inside the container as well as outside it, the containers do not have to be dimensionally stable.
It is an object of the present invention, while maintaining the above mentioned advantages, to simplify the mechanical design and reduce power consumption.
This object has been achieved according to the present invention in that the electrodes also form the evacuable chamber.
As in the above prior art, the electrodes surround the container leaving a gap, which makes possible the formation of a vacuum also outside of the containers, which gap however is so narrow on the other side that no plasma can be ignited in the gap. The plasma is therefore essentially ignited only on the inside of the containers, so that only the inner surfaces of the containers, together with the outer surfaces in the area of the filling opening, are sterilized. This results in a high level of effectiveness. As a result of the electrodes themselves forming the evacuable chamber, and not being arranged in an evacuable reactor, the volume to be evacuated is reduced considerably. The space to be evacuated corresponds therefore essentially only to the inside of the containers to be sterilized, although these themselves do not form the reactor.
In preferred embodiments of the present invention it is provided that both electrodes, with the aid of an intermediary insulator, butt in a sealed manner against each other with a partition line between them.
The electrodes surround the respective container with shell-like areas, which can be moved apart for the insertion of the container into the chamber. Furthermore, the electrodes are provided with extensions which are arranged at the bottom of the container and which are insulated against each other, which extensions are arranged on a non-electroconductive supporting plate, on which the containers stand during the sterilization process. The extensions can also be separated from the shell-like areas of the electrodes.
These and further objects, features and advantages of the present invention will become more readily apparent from the following detailed description thereof when taken in conjunction with the accompanying drawing.